Past experimentation with SCH 52000 demonstrated numerous biological effects on T cells, monocyte-macrophages, neutrophils, B cell proliferation and immunoglobulin production, Lymphokine Activated Killer (LAK), Natural Killer (NK) activity and on mast cell growth and proliferation. The primary objective of this study is to evaluate in a dose-escalating manner, the safety and tolerance of daily subcutaneous (SC) doses of SCH 52000 (0.5, 1.0, 5.0, 10.0, and 20.0 mg/Kg) given for 28 days to patients with active rheumatoid arthritis (RA). The secondary objectives are to evaluate: first, the effect of SCH 52000 on RA measures of disease activity and second, the Ex vivo cytokine levels in stimulated whole blood pre- and during SCH 52000 administration in patients with RA. The study design can be characterized as a phase I, multicenter, randomized double-blind, placebo controlled, rising and multiple dose, safety, and tolerance study. Potential study participants are screened between 3 and 28 days prior to study enrollment. Once enrolled in the study, patients are monitored by the Principal Investigator and followed-up by the study coordinator at the Clinical Research Unit for 10 visits over an 84 day period. Change in disease activity over time is measured at every visit by tender and swollen joint assessments and patient self-administered questionnaires. Lab studies are also conducted at every visit for close monitoring of the patients' response to the study drug. In general, patients appear to be responding well to SCH 52000 with little or no side effects. Since August 1995, of the five patients screened, four were eligible to participate in the study. Only one patient was enrolled in the first dose level and their study outcome was labeled as a treatment failure. However, two of the three patients enrolled in the second dose level felt markedly improved while on the study drug. The first and second dose levels will be completed in January 1996. The two patients recruited and screened for the third dose level in December 1995 were deemed ineligible at the baseline visit. Consequently, no patients were entered in the third dose level at this site. The fourth dose level, which began mid-January 1996, has one patient enrolled. Recruitment for the fifth dose level will take place in January and February 1996.